I. Field
The following description relates generally to content protection, and, amongst other things, to decryption of data.
II. Background
Wireless networking systems have become a prevalent means by which a majority of people worldwide have come to communicate. Wireless communication devices have become smaller and more powerful in order to meet consumer needs and to improve portability and convenience. Consumers have become dependent upon wireless communication devices such as cellular telephones, personal digital assistants (PDAs) and the like, demanding reliable service, expanded areas of coverage and increased functionality.
One such function is the distribution of data intensive content such as video content. Consumers have become used to high levels of service in terms of availability, management, access control and device capabilities based upon their experiences with existing technologies (e.g., television, the Internet). Provision of data intensive content that meets these expectations includes many challenges.
One such challenge is protection of the content during and after distribution. Content providers typically require that a content distribution system have the ability to provide Digital Rights Management (DRM), which refers to any of several technical arrangements that provide control of distributed material on electronic devices with such measures installed. An underlying component for content distribution systems is encryption/decryption of media. DRM software can provide the underlying encryption/decryption algorithms, hashing and authentication algorithm implementations used by both clients and servers. DRM software can also provide for license management and secure storage of content.
DRM can utilize two types of cryptosystems or cryptography techniques, symmetric cryptography and asymmetric cryptography. In symmetric key cryptography, a single key is used for both encryption and decryption of data. Examples of symmetric cryptography algorithms include Data Encryption Standard (DES) and Advanced Encryption Standard (AES) systems. In asymmetric cryptography, also known as public-key cryptography, each user may have a public key and a private key. Encryption is performed with the public key while decryption is performed with the private key. Examples of asymmetric cryptography include the Rivest, Shamir and Adleman (RSA) algorithm and Elliptic Curve Cryptography (ECC). Although decryption utilizing symmetric key cryptography algorithms is significantly faster than decryption utilizing asymmetric key cryptography algorithms, symmetric key cryptography requires communication of shared keys between the communicating entities. In asymmetric cryptography, an entity can distribute its public key to other entities allowing any such entity to encrypt data utilizing the public key. However, the encrypted data can be decrypted only with the private key maintained by the entity that distributed the public key. While asymmetric cryptography is computationally expensive, it does not require secure distribution of shared keys between entities desiring secure communication.